1 /*
2 * Copyright (C) 2007 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14
15 package com.google.common.primitives;
16
17 import static com.google.common.base.Preconditions.checkNotNull;
18
19 import com.google.common.annotations.GwtIncompatible;
20 import java.util.Collections;
21 import java.util.LinkedHashMap;
22 import java.util.Map;
23 import java.util.Set;
24
25 /**
26 * Contains static utility methods pertaining to primitive types and their corresponding wrapper
27 * types.
28 *
29 * @author Kevin Bourrillion
30 * @since 1.0
31 */
32 @GwtIncompatible
33 @ElementTypesAreNonnullByDefault
34 public final class Primitives {
35 private Primitives() {}
36
37 /** A map from primitive types to their corresponding wrapper types. */
38 private static final Map<Class<?>, Class<?>> PRIMITIVE_TO_WRAPPER_TYPE;
39
40 /** A map from wrapper types to their corresponding primitive types. */
41 private static final Map<Class<?>, Class<?>> WRAPPER_TO_PRIMITIVE_TYPE;
42
43 // Sad that we can't use a BiMap. :(
44
45 static {
46 Map<Class<?>, Class<?>> primToWrap = new LinkedHashMap<>(16);
47 Map<Class<?>, Class<?>> wrapToPrim = new LinkedHashMap<>(16);
48
49 add(primToWrap, wrapToPrim, boolean.class, Boolean.class);
50 add(primToWrap, wrapToPrim, byte.class, Byte.class);
51 add(primToWrap, wrapToPrim, char.class, Character.class);
52 add(primToWrap, wrapToPrim, double.class, Double.class);
53 add(primToWrap, wrapToPrim, float.class, Float.class);
54 add(primToWrap, wrapToPrim, int.class, Integer.class);
55 add(primToWrap, wrapToPrim, long.class, Long.class);
56 add(primToWrap, wrapToPrim, short.class, Short.class);
57 add(primToWrap, wrapToPrim, void.class, Void.class);
58
59 PRIMITIVE_TO_WRAPPER_TYPE = Collections.unmodifiableMap(primToWrap);
60 WRAPPER_TO_PRIMITIVE_TYPE = Collections.unmodifiableMap(wrapToPrim);
61 }
62
63 private static void add(
64 Map<Class<?>, Class<?>> forward,
65 Map<Class<?>, Class<?>> backward,
66 Class<?> key,
67 Class<?> value) {
68 forward.put(key, value);
69 backward.put(value, key);
70 }
71
72 /**
73 * Returns an immutable set of all nine primitive types (including {@code void}). Note that a
74 * simpler way to test whether a {@code Class} instance is a member of this set is to call {@link
75 * Class#isPrimitive}.
76 *
77 * @since 3.0
78 */
79 public static Set<Class<?>> allPrimitiveTypes() {
80 return PRIMITIVE_TO_WRAPPER_TYPE.keySet();
81 }
82
83 /**
84 * Returns an immutable set of all nine primitive-wrapper types (including {@link Void}).
85 *
86 * @since 3.0
87 */
88 public static Set<Class<?>> allWrapperTypes() {
89 return WRAPPER_TO_PRIMITIVE_TYPE.keySet();
90 }
91
92 /**
93 * Returns {@code true} if {@code type} is one of the nine primitive-wrapper types, such as {@link
94 * Integer}.
95 *
96 * @see Class#isPrimitive
97 */
98 public static boolean isWrapperType(Class<?> type) {
99 return WRAPPER_TO_PRIMITIVE_TYPE.containsKey(checkNotNull(type));
100 }
101
102 /**
103 * Returns the corresponding wrapper type of {@code type} if it is a primitive type; otherwise
104 * returns {@code type} itself. Idempotent.
105 *
106 * <pre>
107 * wrap(int.class) == Integer.class
108 * wrap(Integer.class) == Integer.class
109 * wrap(String.class) == String.class
110 * </pre>
111 */
112 public static <T> Class<T> wrap(Class<T> type) {
113 checkNotNull(type);
114
115 // cast is safe: long.class and Long.class are both of type Class<Long>
116 @SuppressWarnings("unchecked")
117 Class<T> wrapped = (Class<T>) PRIMITIVE_TO_WRAPPER_TYPE.get(type);
118 return (wrapped == null) ? type : wrapped;
119 }
120
121 /**
122 * Returns the corresponding primitive type of {@code type} if it is a wrapper type; otherwise
123 * returns {@code type} itself. Idempotent.
124 *
125 * <pre>
126 * unwrap(Integer.class) == int.class
127 * unwrap(int.class) == int.class
128 * unwrap(String.class) == String.class
129 * </pre>
130 */
131 public static <T> Class<T> unwrap(Class<T> type) {
132 checkNotNull(type);
133
134 // cast is safe: long.class and Long.class are both of type Class<Long>
135 @SuppressWarnings("unchecked")
136 Class<T> unwrapped = (Class<T>) WRAPPER_TO_PRIMITIVE_TYPE.get(type);
137 return (unwrapped == null) ? type : unwrapped;
138 }
139 }